Tool control

ABSTRACT

System for control of tool drive with respect to at least X and Y axes to trace a first path segment and to approach a second path segment (e.g., for tool offset, or to trace an inscribed curve tangent to the two path segments), by steps comprising storage of data descriptive of X and Y positions corresponding to current X and Y tool positions and of a first function the value of which is dependent upon the perpendicular distance from the X and Y positions to the second path segment, updating of the stored data upon advance of the drive during the tracing of the first path segment, and interruption of the tracing of the first path segment when the function assumes a predetermined value.

United States Patent 1191 [111 3,770,947 Deily 1451 Nov. 6, 1973 TOOL CONTROL 3,500,150 3/1970 Foster 318 572 [75] Inventor: Don Delly, Lexington, Mass. Primary Examiner Eugene G Botz [73] Assignees: City National Bank of Detroit, Assistant Examiner-Jerry Smith Detroit, Mich.; Robert C. Fisher AttorneyJ0hn N. Williams [22] Filed: Aug. 20, 1971 [57] ABSTRACT [21] PP NO-I 173,408 System for control of tool drive with respect to at least X and Y axes to trace a first path segment and to ap- 52 us. Cl 235/151.11, 235/152, 318/572, P 9"? Path Segment -1 for Offset, of

318/573 to trace an inscribed curve tangent to the two path seg- 5 1] Int. Cl. G06f 15/46 men), by stepsfiomprising g of data descriptive [58] Field of Search 235/151.11, 152; of X and Posmcms 9 Current X and 318561569470, 572 574 Y tool posmons and of a first function the value of which 18 dependent upon the perpendicular distance [56] References Cited frocrln the Xfanhd Y posiitigns to the segond patlt tiegmient, UNITED STATES PATENTS up atmg o t e store ata upon a vance 0 e rive during the tracing of the first path segment, and intergekrFhenmcdcr ruption of the tracing of the first path segment when c 1 3,416,056 12/1968 Motooka et al. 318 573 the funct'on assumes a predetermmed Value 3,423,656 H1969 Tripp 318/570 8 Claims, 23 Drawing Figures j COMPUTER I 5O 22 0 1 7901 m 6O 34 i PM 62 p M 3 W i l 5X 38 l AX 4O 5M w 1 SF 5 i l ADD/SUBTRACT 44 l PAIENTEDMJV 6 ma 3770.947 Y sum 030F 20 v PAIENTEDNM 6 ma v saw one; 20

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1. A method for control of a tool drive with respect to at least X and Y axes to trace a first path segment and to approach a second path segment, by steps comprising storage of data descriptive of X and Y positions corresponding to current X and Y tool positions and of a first function the value of which is dependent upon the perpendicular distance from said X and Y positions to said second path segment, updating of the stored data upon advance of said drive during the tracing of said first path segment, and interruption of the tracing of said first path segment when said function assumes a predetermined value different from zero.
 2. The method of claim 1 wherein said predetermined value corresponds to a desired tool offset for said second path segment, and said X and Y positions are said current tool positions.
 3. The method of claim 1 wherein said X and Y positions are pseudo tool positions on a pseudo path segment parallel to said first path segment and intersecting the center of an inscribed curve to be traced tangent to said first and second path segments, and said predetermined value corresponds to the distance between said first and pseudo path segments.
 4. The method of claim 3 wherein said inscribed curve is a circular arc, and said pseudo path segment is spaced from said first path by the radius of said arc.
 5. The method of claim 1 wherein said tracing of said first path segment is interrupted when the value of said function changes its algebraic sign.
 6. The method of claim 1 wherein the stored value of said function is updated according to the following table, where said second path segment is a line segment between points (X1, Y1) and (X2, Y2), and said function is of the form H Delta X.Y Delta Y.X + (X1.Y2-X2.Y1), where Delta X X2-X1 and Delta Y Y2-Y1: UNIT DRIVE ADVANCE VALUE OF H UPDATING +X - Delta Y +Y + Delta X -X + Delta Y -Y - Delta X
 7. The method of claim 1 wherein the stored value of said function is updated according to the following table, where said second path segment is a circular arc having a center (XC, YC) and endpoints (X1, Y1), (X2, Y2), and said function is of the form H (X-XC)2 + (Y-YC)2: UNIT DRIVE ADVANCE VALUE OF H UPDATING +X +2(X-XC) + 1 +Y +2(Y-YC) +1 -X -2(X-XC) + 1 -Y -2(Y-YC) + 1
 8. The method of claim 1, said steps further comprising storage of additional data descriptive of a second function the value of which is dependent upon the perpendicular distance from current tool position to said first path segment, updating of the additional stored data upon advance of said drive during the tracing of said first path segment, and control of said advance so that the value of said second function tends toward a predetermined constant value corresponding to a desired tool offset. 